Investigation of the Wettability and the Heat Transfer on Laser-Manufactured Complex Surfaces during Vapour Condensation at Saturated and Superheated Condition

本课题的主要任务是利用激光制造技术系统地、选择性地对过冷基板的表面质量进行修饰，使蒸汽冷凝过程中的散热得到显著改善。值得注意的是，与未修饰的表面相比，在相同的操作条件下，散热的增加是实现的。在拟议的研究项目框架中，它打算使用一个光滑的、非结构化的参考表面以及几个由铝和铜制成的微结构表面。关于接触角的扩大，除了应用激光制造技术外，表面还要进行电化学处理。通过这一步骤，在表面上实现纳米结构，这将导致表面能的降低和液壁边界处的接触角的增大，从而最终实现传热的强化。从实验中，确定影响因素（接触角/滞后、表面粗糙度、操作压力等），可以显著影响整个冷凝过程，将通过对传热和表面润湿的时间和空间高分辨率测量来确定，并显示它们与地形变化的相互依赖性。此外，纳米微观结构对传热和润湿特性的贡献应该通过测量值进行数学建模，并与现有的文献和实验数据进行验证。

The main task in this project is to systematically and selectively modify the surface quality of sub-cooled substrates by means of laser manufacturing technology, such that a significant improvement in heat dissipation during steam condensation is achieved. It should be noted that, compared with non-modified surfaces, the increase in heat dissipation is achieved at equivalent operating conditions.In the frame of the proposed research project it is intended to use a smooth, unstructured reference surface as well as several microstructured surfaces made of aluminum and copper. With regard to the contact angle enlargement, the surfaces are subjected to an electrochemical treatment in addition to the application of the laser manufacturing technique. Through this step, a nanostructuring is to be achieved on the surfaces, which should lead to reduced surface energy and larger contact angles at the liquid-wall boundary, in order finally to achieve an intensification of the heat transfer.From the experiments, determining influencing factors (contact angle / hysteresis, surface roughness, operating pressure, etc.), which can significantly influence the entire condensation process, will be identified by temporally and spatially high-resolved measurements on heat transfer and surface wetting and their interdependencies with respect to topography changes will be shown. Furthermore, the contribution of nano-micro-structures on heat transfer together with the wetting characteristics should be modelled mathematically by using of measured values and should be validated with the available literature and experimental data.